1. Field of the Invention
This present invention relates to motor vehicles.
2. Description of the Prior Art
Present interest is in making surface transportation vehicles that would move at high speeds without need for the high power required by familiar vehicles. Configurations from the aircraft world offer large benefits if appropriate measures are taken to fully utilize their aerodynamic performance, and doing this entails unconventional apparatus that is not a part of the conventional ground vehicle world. Given the present day problems with energy, failure to utilize the incredibly low aerodynamic drag of the well known airship in ground vehicles is a glaring failure to innovate.
The present invention is discussed here in reference to existing transportation systems. Traditional design activities address aerodynamic drag force, rolling resistance drag force, and dynamic effects of lateral forces due to handling and cross wind situations. Aerodynamic drag force impedes motion in the intended travel direction. Cross wind aerodynamic force is among the destabilizing lateral forces that also include side forces on wheels that arise in real operational situations. The term lateral means a direction parallel to the surface and perpendicular to the travel direction. A longitudinal vehicle axis is parallel to direction of travel. Airship experience has often been applied to the motor vehicle world, especially that of the automobile, but this work has always stopped short of taking the necessary measures to fully exploit this opportunity.
Strictly speaking, the field of the invention would better be described as heat engine driven vehicles since that is by far the most common situation. This distinction is quite often ignored, but this can lead to serious error. In this document the term engine is generally used since it is the relevant large mass of equipment in most cases. Electric traction motors and batteries can perform similarly, but the mass distribution issues are entirely different. Any apparatus that delivers propulsion energy is an equivalent to the engine specified here.
The heat engine is not a precisely defined article in context of present day concerns about fuel economy and fuel types. It also is somewhat variable in size, being subject to measures to reduce the need for power from such an engine which then dictates smaller mass.
There is much to overcome in the tradition of motor vehicles. Conventional automotive wisdom dictates a bluff body, that descriptive term meaning that the front and rear are much more abrupt than would be appropriate in a serious aerodynamic situation such as that encountered by aircraft. Perhaps this became a fixed tradition since cars evolved from horse drawn carriages where aerodynamic shape was not critical due to relative slow speeds involved. Even the Model T Ford design ignored aerodynamics, and this was due to both relatively low speed for most uses and inexpensive fuel supplies. Public taste is firmly aligned with the familiar; thus the bluff foolishness is well entrenched.
This bluff body limits possibilities to achieve effective aerodynamic operation. The limits of aerodynamic refinement of the bluff body were largely realized in the first decades after the Model T Ford. It seems there was little motivation to raise the vehicle above the ground to improve airflow; in fact, once that bluff body idea is accepted, the better course of action may be to reduce ground clearance. Of course, the stability issues of a high vehicle would probably have been seen as insurmountable, and thus excluded any idea of such a possibility.
Furthermore, it has been a rarely challenged rule that any car must provide side by side seating for at least two adults. This conventional thinking has long precluded aerodynamic progress anywhere close to that which is possible.
An exception to the bluff body was attempted with the studies by A. Morelli reported in “Impact of Aerodynamics on Vehicle Design”, Proceedings of the International Association for Vehicle Design, SP-3, p. 70-98 (1983). A. Morelli was actually studying shapes that would enable operating a vehicle close to the ground, as demanded by the automotive world, yet would perform similarly to ideal aerodynamic bodies based on the teardrop shape. Morelli also accepted, as a fundamental requirement, that side-by-side seating must be provided for in a car.
The concept developed by A. Morelli was successfully shown to achieve the airship level of aerodynamic drag using an idealized model in wind tunnel tests. While the resulting form was consistent with the width requirement for side-by-side seating, the resulting form was very inefficient in load carrying volume considering its overall length. This inefficiency was due to the rapid taper of the basic teardrop shape as well as the camber that he added to cut down on vortices. Neither did the benefits carry through very well when actual wheels were attached. Though it was a significant attack on the bluff body tradition, it seems to have gone by mostly un-noticed, though a recent high efficiency vehicle known as the Aptera is an exception.
We know it is theoretically possible to do many times better, based on the airship tradition. This is notably represented by wind tunnel studies of the USS Akron by Hugh B. Freeman reported in NAC Report No. 432. The requirement for free flow aerodynamic conditions is very apparent from observation of the measurement procedures used in these studies. Wind tunnels are far larger than the models so that floor, walls, and ceiling are much separated from the models under test.
Without being focused on aerodynamics as such, searching for a way to make a closed car that would give the advantages of a motorcycle without the hazards of such, led to U.S. Pat. No. 7,338,061 Bullis, Mar. 4, 2008. This provided a wheel system that makes a narrow motor vehicle stable. An unexpected benefit of this approach was a remarkably stable steering process that developed out of the articulated arrangement of this prior invention. The reduced frontal area immediately results in reduced aerodynamic drag, which would be applicable to whatever shaping would then be implemented. Further development of this concept using known aerodynamic concepts showed that major improvements in aerodynamic efficiency were possible. These included measures to shape the main vehicle body for low aerodynamic drag, together with measures that elevated the passenger carrying body above the roadway such that the shaped body would perform like it would in free flow conditions. Patent application Ser. No. 11/893,497 Bullis, Aug. 16, 2007 discloses such apparatus. Thus it was found that the unusual stabilizing features as specified in that previous U.S. Pat. No. 7,338,061 Bullis, Mar. 4, 2009 could serve both to enable a narrow vehicle and to enable an elevated aerodynamic body of that vehicle. This was a major breakthrough in the design of efficient transportation systems.
In application Ser. No. 11/893,497 Bullis, Aug. 16, 2007 the stabilizing apparatus involved various wheel arrangements to prevent roll-over situations. Such wheel arrangements involved wheels offsetting to an outside of a turn that enabled increased, roll resisting torque. In particular, the front wheels of these vehicles were not used to initiate turns. Also noted were configurations providing judiciously placing equipment of significant weight into wheel train arrangements aligned with wheels that also minimized roll-over hazards. Weight distribution in the upper, elevated aerodynamic body was not addressed in detail.
Also discussed in application Ser. No. 11/893,497 Bullis, Aug. 16, 2007 were measures whereby tall vehicles which resulted from elevated body arrangements that were subject to cross wind hazards could be made less vulnerable by minimizing forces due to lateral air flow.
Beyond the world of automobiles, much of the energy used in transportation is used by heavy truck transportation. Applications that would improve efficiency of larger vehicles such as trucks were limited with the stabilizing arrangement of U.S. Pat. No. 7,338,061 Bullis, Mar. 4, 2008, because it involved a two axis joint where the two axes were offset. This offset arrangement entails significant structure to transfer heavy loads through that joint. Even for lighter vehicles, there is a weight penalty due to the offset arrangement. The arrangements also tended to have an affect on turning radius that was somewhat limiting for cars, but especially for long trucks.
The large truck represents the most significant opportunity to save energy. The engine part of such vehicles is normally low for overall stability reasons, so aerodynamic flow under that part of the vehicle is limited. The more rearward airflow is fully turbulent beyond that. Worse still is the fact that the very common large semi-trucks actually present a double aerodynamic event due to the separation of the tractor and trailer parts.
Heavy trucks are also subject to significant energy loss due to a different mechanism. Adding to aerodynamic drag effects, there is a friction like loss that is mostly due to rolling resistance of rubber wheels on paved roads. Patent application Ser. No. 12/454,745 Bullis, May 21, 2009 disclosed a hybrid wheel system that nearly eliminates rolling resistance of highway truck wheels when operating on steel rails placed on a paved roadway, yet have full capability to operate when the steel rails are absent. That same application discussed, as prior art, railroad service vehicles adapted to run on railroad rails or paved roads as alternatives. With the hybrid wheel system the shift from operation on rails to operating on paved surfaces is accomplished by the combined wheels having available sizes that simply take over as appropriate for respective surfaces, be they rail or paved surface.
Rear engine vehicles or mid engine vehicles are known. These include the originally imported Volkswagen car, Volkswagen buses and vans, Porsche sports cars, Toyota MR2 and such which are exceptions to the more general front engine vehicle. None of these broke the traditional design rule that the car should be as low as possible to the road, except perhaps the Volkswagen bus. The box-like form of the Volkswagen bus was shaped for utility such that it would not qualify as an aerodynamic body. It is, however, a remarkably high vehicle given its standard wheel base width. It is often thought that stability is due to the relatively low engine that is a flat block form. It is obvious that this low engine would give meaningful degree of stabilization in a constant radius turning condition. Not obvious is the advantage of the rear position of that engine, away from the pivoting wheels that control vehicle direction.
The trailer part of most large semi-trucks is notably high above the road. Stability is obviously a manageable issue for these articulated vehicles. In contrast the engine in the tractor part is set quite low to the ground. The low engine is somewhat relevant to how the trailer load is stabilized, but it seems that proximity of this mass near to the front wheels makes it particularly important to keep it low. Though there have been attempts to smooth the transition between tractor and trailer, the basic tractor trailer arrangement is about as wrong aerodynamically as it could be. Both tractor and trailer are the most bluff of bluff bodies and the combination represents two, almost separate, aerodynamic casualties.